CS125 in RS485 mode on a CR-Basic Datalogger

I would like to control and log data from a CS125 on a CR1000X (CS 125 POLL mode). I would like to use a longer (120 m) cable through the RS 485 instead of the RS 232 protocol.

What is the corrrect setting for the serial-open command on a CR1000X for teh RS485 mode? I tried "SerialOpen (ComC7,38400,3,0,1000,3)" with the CS125 in RS485 Mode, but I am not sure if the option "3" is correct. I cannot communicate. Same program works with "SerialOpen (ComC7,38400,3,0,1000)" and the CS125 set to RS232. Both options just have a short cable for testing. Same wiring. Anything else to consider? Anything I did wrong?